In the creation of an urban model or the like, an outline of a roof (including a rooftop) of a building is recognized by using high-resolution aerial photograph imagery taken from an aircraft or the like. Conventional methods therefor include a method in which a structure of a building roof outline is determined from a stereographic image by a worker using a stereo plotter, a semiautomatic recognition method in which a worker specifies a range in which the outline of the building exists and the building roof outline is generated within the range by image recognition processing, and a method in which the worker recognizes the building roof outline from an orthoimage (orthographic projection image) by heads-up digitizing.
Further proposed are a method of automatically recognizing the building roof outline by using an aerial photograph image and a method of automatically recognizing the building roof outline by using digital surface model (DSM) data.